Experimental plots were overlaid on commercial fields of broccoli (Brassica oleraceae L. var. Italica) and cauliflower (Brassica oleraceae L. var. botrytis L.) to evaluate legume species as interseedings in vegetable production. White clover (Trifolium repens L.), red clover (T. pratense L.), yellow sweet clover (Melilotus officinalis L.), hairy vetch (Vicia villosa Roth.) and crimson clover (T. incarnatum L.) were seeded 4-5 weeks after an early planting of broccoli and a late planting of cauliflower. Crop yields, forage biomass, weed biomass and percent fall ground cover were recorded. / A dry year coupled with difficulties in applying the treatments resulted in low forage biomass. Hairy vetch yielded the most within the early broccoli planting system. High rainfall the next year resulted in high biomass yields. Over the two year study, hairy vetch and crimson clover emerged as the two most productive species. Significant effects on fall weed biomass were observed with broccoli in the second year of the study, where interseeded plots reduced weed populations by at least 66%. No evidence was seen of weed suppression by interseedings prior to harvest. Crop yields were not affected by interseedings. All interseeded treatments provided the minimum of 30% ground cover required to help reduce erosion.

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Agricultural systems are known to emit nitrous oxide (N2O)---a potent greenhouse gas. The roving flux tower measuring system of Agriculture and Agri-Food Canada was used to make continuous measurements of N2O fluxes in an edible pea field in Western Quebec in 2003-04 and then in an alfalfa-timothy forage field in Eastern Ontario in 2004-05. The experiment was designed to capture, at the field scale, the expected large N2O emissions occurring as a result of fertilizer application for a year, in relation to both large precipitation events and spring thaw. / Growing season N2O emissions averaged 0.5 to 5 mg N2 O-N m-2 d-1 with peaks following snow melt (between 5 and 8 mg N2O-N m-2 d-1) and manure applications (8 to 37 mg N2O-N m-2 d -1). Although generally small (<0.25 mg N2O-N m -2 d-1), emissions were detectable during the fall and winter, indicating the importance of including them in annual emission totals. / The measurements were used to verify the performance of the simulation model DNDC (DeNitrification-DeComposition) in estimating N2O emissions from legumes and in response to dairy manure application. Sensitivity tests were also carried out in which baseline input values were modified. Results suggest that the current model version (DNDC8.9) requires further modification prior to application for estimating greenhouse gas emissions in national accounting systems.